Auto makers signaled their hot streak in the U.S. is rapidly cooling, as demand last month turned surprisingly sluggish for the trucks and SUVs that have fueled record profits for domestic players.

General Motors Co. and Ford Motor Co. on Tuesday reported declines in April of 5.8% and 7.1%, respectively, compared with the same month last year. Fiat Chrysler Automobiles NV reported a 7% decline, as sales at its Jeep brand continued to tumble.